Discharge lamp starter device

ABSTRACT

A discharge lamp starter device adapted to instantaneously light a fluorescent discharge lamp, in which a reverse blocking diode thyristor is connected in parallel with a fluorescent discharge tube, the reverse blocking diode thyristor having a breakdown voltage (VBO) lower than the rated voltage of the power source but higher than the discharge voltage of the fluorescent discharge tube while having a blocking voltage (VR) of a value sufficiently greater than the breakdown voltage (VBO).

United States Patent [72] Inventors Tflru Tfl t l [50] Field ol'Search 315/100 H, Osaka; 98, 99, 100 Yasutaka Kawai, Higashiosaka-shi; Takeshl Matsushima. Nara-shi; Shlgeo 56] References Cited Koyama, Neyagawa-shi; Kenji Shimatani, UNITED STATES PATENTS flirk'u'shivahmalan 2,861,219 11/1958 Knobel. 315/100x 5;; f 3332 2,871,409 1/1959 Aldrich m1. 315/99 1 e 45 1 Patented June 8,1971 FOREIGN MT [73] Assign M t hit m-1 Industrial Co, Ltd, 912,181 12/1962 Great Br1ta1n 3l5/100(H) Kadoma'shi Osaka Primary ExaminerRoy Lake [32] Pnomy 1968 Assistant ExaminerDarwin R. Hostetter 137;; Attorney-Stevens, Davis, Miller and Mosher ABSTRACT: A discharge lamp starter device adapted to instantaneously light a fluorescent discharge lamp, in which a reverse blocking diode thyristor is connected in parallel with a [54] ggg f LAIMPgTARTER DEVICE fluorescent discharge tube, the reverse blocking diode raw thyristor having a breakdown voltage (V lower than the [52] U.S. Cl 315/99, rated voltage of the power source but higher than the 315/100 DIG. 2 discharge voltage of the fluorescent discharge tube while hav- [51] Int. Cl. H05b41/04, ing a blocking voltage (V of a value sufficiently greater than H05b 41/14 the breakdown voltage (V W I-w 1 emigre DISCHARGE LAMP STARTER DEVICE This invention generally relates to a discharge lamp starting device, and more particularly to such starter device adapted to instantaneously start a fluorescent discharge lamp, in which a reverse blocking diode thyristor is connected in parallel with a fluorescent discharge tube, the reverse blocking diode thyristor having a breakdown voltage lower than the voltage of the power source but higher than the discharge voltage of the fluorescent discharge tube while having a blocking voltage of a sufficiently higher value than the breakdown voltage, and use is made of a cathode preheating winding wound in a magnetic circuit common to a ballast.

In the conventional discharge lamp starter devices, as shown in FIGS. 1 and 2, the lamp was lighted by the parallel connection of a fluorescent discharge tube I and a manual switch 2 or a glow starter 3. The device using a manual switch required much time for starting, and the device using a glow starter required less time for starting but suffered from the problem of a shorter life resulting from the use of the glow starter. The known starter devices of FIGS. 1 and 2 further include an AC power source 4, a power source switch 5, and a ballast 6. A noisepreventing capacitor 7 is connected in parallelwith the manual switch 2 or the glow starter 3 to prevent the occurrence of noises in the discharge tube 1.

The present invention therefore intends to eliminate the above-mentioned drawbacks existing in the prior art discharge lamp starter devices.

The object of the present invention is to provide a novel discharge lamp starter device which is characterized by a power source having one terminal thereof connected with one end of one of the cathodes of a fluorescent discharge tube through a ballast, the other terminal of the said power source being connectedwith one end of the other cathodeof said discharge tube, a cathode preheating winding wound in a magnetic circuit common to the ballast for the saturation of the said magnetic circuit, and a reverse blocking diode thyristor having a breakdown voltage lower than the rated voltage of the power source but higher than the discharge voltage of the discharge tube and having a blocking voltage sufficiently higher than the rated voltage of the power source, said cathode preheating winding and said reverse blocking diode thyristor being connected together in series between the other ends of the respective cathodes of said fluorescent discharge tube.

According to the present invention there are provided various advantages over the prior art. As the starter means, use is made of a semiconductor element in lieu of a glow starter, and this leads to the advantages such as semipermanent life and much smaller size of the discharge lamp starter device. Also a quick starting is accomplished by the operation of the semiconductor element and the cathode preheating winding. The semiconductor element, which performs electrical switching action, imparts much less damage to the fluorescent discharge tube than the glow starter or manual switch-type. Furthermore, the parallel connection of the capacitor with the power source enables the prevention of noises in the discharge tube. These advantages in turn result in a great industrial advantage.

Other objects, features and advantages of the present invention will be readily apparent from the following description with respect to the accompanying drawings, in which:

FIGS. 1 and 2 are electric circuit diagrams of the discharge lamp starter devices according to the prior art;

FIG. 3 shows the electric circuit diagram of the discharge lamp starter device according to an embodiment of the present invention;

FIG. 4 is a graph illustrating the voltage-current characteristic of the reverse blocking diode thyristor used in the device of FIG. 3;

FIG. 5 is a graph illustrating the waveform of the voltage applied across the terminals a and b of the reverse blocking diode thyristor;

FIG. 6 is a graph showing the waveform of the current passing through the reverse blocking diode thyristor during the cathode preheating; and

FIGS. 7, 8 and 9 illustrate the voltage-current characteristics of the symmetrical diode thyristor, diode and another type of a reverse blocking diode thyristor, respectively, which are used to obtain the characteristic as shown in FIG. 4.

The invention will now be described with respect to an embodiment thereof in conjunction with FIGS. 3 to 9.

Referring to FIG. 3, there are shown an AC power source 8, a noise preventing capacitor 9, a power source switch 10, a ballast II, a cathode preheating winding I2 wound in a magnetic circuit common to the ballast 11, a fluorescent discharge tube 13 having cathodes 14 and 15 provided at the opposite ends thereof, and a reverse blocking diode thyristor 16. The reverse blocking diode thyristor 16 has such a switching characteristic, as shown in FIG. 4, that is changes from the eutoff state to the conductive state when a predetermined forward voltage (hereinafter referred to as breakdown voltage V is reached. The reverse blocking diode thyristor 16 used in the starter device of FIG. 3 is also of such a characteristic that the relation of rated output voltage of power source 8 breakdown voltage V, terminal voltage of discharge tube 13 is satisfied while the relation of blocking voltage V rated output voltage of power source 8 is also satisfied. Such reverse blocking diode thyristor is connected with the discharge tube 13. The reverse blocking diode thyristor having the characteristic as shown in FIG. 4 may also be provided, for example, by the series connection of a symmetrical diode thyristor satisfying the said first relation as shown in FIG. 7, with a diode whose blocking voltage V has a sufficiently higher value than the rated power source voltage as shown in FIG. 8. Alternatively, the reverse blocking diode thyristor 16 having a same characteristic as shown in FIG. 4 may be provided by connecting a conventional reverse blocking diode thyristor,'instead of the symmetrical diode thyristor as shown in FIG. 7, having substantially the same characteristic that the forward breakdown voltage V equals the opposite blocking voltage V, as shown in FIG. 9, in series and in the same direction with a diode as shown in FIG. 8.

The circuit arrangement of the discharge lamp starter device according to the present invention is such that the noise preventing capacitor 9 is connected in parallel with both terminals of the power source 8 through the power source switch 10 and one terminal of the power source 8 is connected with one end of the cathode 14 of the discharge tube 13 through the ballast ll while the other terminal of the power source 8 is connected with one end of the other cathode 15 of the discharge tube 13 through the power source switch 10. The other end of the cathode 14 is connected with one end of the reverse blocking diode thyristor through the cathode preheating winding 12, and the other end of the cathode 15 is connected directly with the other end of the reverse blocking diode thyristor 16. During the preheating of the cathodes l4 and 15 insufficient preheating occurs since the half-wave of the opposite direction is blocked as seen from the abovedescribed characteristic of the reverse blocking diode thyristor 16. In order to compensate for such insufficiency of the cathode preheating current, the cathode preheating winding I2 is wound in the magnetic circuit common to the ballast 11 to thereby saturate the magnetic circuit and accordingly reduce the impedance of the circuit so as to derive sufficient cathode preheating current.

The operation of the electric circuit of the starter device according to the present invention will now be described. In the circuit arrangement as shown in FIG. 3, when the power source switch 10 is turned on, a voltage higher than the breakdown voltage V namely the rated output voltage of the power source 8 is applied across the terminals a and b of the reverse blocking diode thyristor 16 and thereby the reverse blocking diode thyristor 16 breaks down during a positive half-wave period and is rendered conductive. Due to the effect of the cathode preheating winding 12 which is a compensating winding wound on the ballast as previously described, and due to the fact that the halfwave rectified current flowing through the circuit includes a DC component, the magnetic circuit is saturated and the impedance of the ballast 11 is also reduced. so that a sufiicient preheating current can be fed to the cathodes l4 and 15 of the discharge tube 13. When a voltage of negative half cycle is applied across the terminals a and h, the reverse blocking diode thyristor does not break down and the power source voltage is applied across the discharge tube 13 to make it ready to be lighted. During the cathode preheating, the waveform of the voltage applied across the terminals and b of the reverse blocking diode thyristor l6 and the waveform of the current passing through the reverse blocking diode thyristor 16 are as shown in FIGS, 5 and 6 respectively. The turnoff of the reverse blocking diode thyristor 16 which is now in the conductive state is determined by the current flowing through the thyristor 16. In this circuit, the current is delayed with respect to the voltage due to the inductances of the ballast 11 and the cathode preheating winding 12, so that part of the negative half-wave is conducted as shown in FIG. 5, In the lighted state, the voltage across the terminals a and b of the reverse blocking diode thyristor is equal to the discharge voltage of the discharge tube 13, and therefore the reverse blocking diode thyristor 16 is brought into the cutoff state. Thus the discharge tube 13 can maintain its discharge,

If the noise preventing capacitor connected in parallel with the starter means according to the prior art is employed in the case wherethe reverse blocking diode thyristor 16 is used as the starter means as in the present invention, and if the device is used under very exacting conditions, such as high supply voltage and low ambient temperature, the charge and discharge of the noise preventing capacitor might impart a pulse voltage higher than the breakdown voltage V, across the thyristor 16 while the discharge tube 13 is being lighted, ad this might occasionally cause the thyristor 16 to be reignited. For this reason, a capacitor 9 of about 0.06 to 0.2 #F. serted between the input of the ballast l1 and the output of the cathode of the fluorescent discharge tube 13, that is, between points 0 and d, as shown in FIG. 3, to thereby attain is inthe same effect as provided by the prior art.

What we claim is:

l. A discharge lamp starter device characterized by a power source having one terminal thereof connected with one end of one cathode ofa fluorescent discharge tube through a ballast, the other terminal of said power source being connected with one end of the other cathode of said discharge tube, a cathode preheating winding wound in a magnetic circuit common to said ballast for the saturation of said magnetic circuit, and a reverse blocking diode thyristor having a breakdown voltage lower than the rated voltage of the mwer source but higher than the discharge voltage of the discharge tube while having a blocking voltage higher than the rated voltage of the power source, said cathode preheating winding and said reverse blocking diode thyristor being connected together in series between the other ends of the respective cathodes of said fluorescent discharge tube.

2. A discharge lamp starter device as defined in claim 1, wherein a noise preventing capacitor is connected in parallel with said power source.

3. A discharge tube starter comprising, in combination, power source terminals, a fluorescent discharge tube with opposite cathodes one end of one cathode of which is connected through a switch with one of said terminals, ballast winding connected between one end of the other of said cathodes and the other of said terminals, a cathode preheating winding wound in a magnetic circuit common to said ballast winding for causing magnetic saturation of said magnetic circuit, and a reverse blocking diode thyristor means having in its forward direction a breakdown voltage lower than the rated voltage of the power source but higher than the discharge voltage of said tube and having in the reverse direction a blocking voltage higher thansaid rated voltage to secure its cutoff state, said cathode preheating winding and said reverse blocking diode thyristor means connected in series between the other end of said one cathode and the other end of said other cathode of the tube to thereby enhance preheating effect to the tube due to the magnetic saturation by said preheating winding and the half-wave rectification of said thyristor means. 

1. A discharge lamp starter device characterized by a power source having one terminal thereof connected with one end of one cathode of a fluorescent discharge tube through a ballast, the other terminal of said power source being connected with one end of the other cathode of said discharge tube, a cathode preheating winding wound in a magnetic circuit common to said ballast for the saturation of said magnetic circuit, and a reverse blocking diode thyristor having a breakdown voltage lower than the rated voltage of the power source but higher than the discharge voltage of the discharge tube while having a blocking voltage higher than the rated voltage of the power source, said cathode preheating winding and said reverse blocking diode thyristor being connected together in series between the other ends of the respective cathodes of said fluorescent discharge tube.
 2. A discharge lamp starter device as defined in claim 1, wherein a noise preventing capacitor is connected in parallel with said power source.
 3. A discharge tube starter comprising, in combination, power source terminals, a fluorescent discharge tube with opposite cathodes one end of one cathode of which is connected through a switch with one of said terminals, ballast winding connected between one end of the other of said cathodes and the other of said terminals, a cathode preheating winding wound in a magnetic circuit common to said ballast winding for causing magnetic saturation of said magnetic circuit, and a reverse blocking diode thyristor means having in its forward direction a breakdown voltage lower than the rated voltage of the power source but higher than the discharge voltage of said tube and having in the reverse direction a blocking voltage higher than said rated voltage to secure its cutoff state, said cathode preheating winding and said reverse blocking diode thyristor means connected in series between the other end of said one cathode and the other end of said other cathode of the tube to thereby enhance preheating effect to the tube due to the magnetic saturation by said preheating winding and the half-wave rectification of said thyristor means. 